For some reason add_hfyu_median_prediction_cmov is only selected
on 3Dnow-capable CPUs, even though it uses no 3Dnow instructions.
This patch allows it to be selected on any cpu with cmov with the
possibility of being overridden by the mmxext version.

This disables the following warnings:
C4100: unreferenced formal parameter
(1035 occurrances)
C4214: nonstandard extension used : bit field types other than int
(609 occurances)
C4996: 'avpriv_snprintf': This function or variable may be unsafe.
Consider using _snprintf_s instead. To disable deprecation,
use _CRT_SECURE_NO_WARNINGS. See online help for details.
(351 occurrances)